Storing slides

I just got my first ever batch of slides back. I'm really happy with the positive image; it's really exciting. But they came back mounted and in a plastic box. It's pretty big. Not terribly big, but if you shot a lot of slides, they would start to take up a lot of space. I want to start thinking about organization now. I know you can buy plastic slide sheets just like negative sheets, and store the slides in binders. This is what I do with my negatives but the standard sheets hold 20 slides. What do you do prefer for storage?